JPS6049165B2 - How to separate esters and ketones - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating a mixed solvent containing an ester and a ketone, and more specifically, the present invention relates to a method for separating a mixed solvent containing an ester and a ketone, and more specifically, the present invention relates to a method for separating a mixed solvent containing an ester and a ketone. The present invention relates to a method for separating an acetate ester and a ketone from a mixture of the acetate ester and the ketone, which is difficult to separate due to the formation of a mixture.

With the recent progress in industry, alcohols, esters, and ketones, which are highly valuable as solvents, are being used singly or as a mixture in a wide variety of fields.

Among these, esters and ketones, especially acetate esters and ketones with 4 to 6 carbon atoms, represented by ethyl acetate and methyl ethyl ketone, are used as intermediate products in the petrochemical industry, as well as in plastic processing, synthetic leather, photographic film, and magnetism. It is widely used industrially in tape manufacturing, textile plants, etc., and large quantities of these solvents are discharged as a mixture along with other solvents. Generally, these solvents are collected as exhaust gas from various parts of a factory and recovered as a mixed solvent by adsorption. The mixed solvent can be reused as it is or after adjusting its composition, but since the recovered mixed solvent contains decomposition products and impurities, it is desired to separate and purify it. Nevertheless, no economical method for separating mixtures of acetate and ketones has been established to date.
When using a mixture of esters and ketones, they are often used with the same number of carbon atoms from the viewpoint of volatility.
As a typical example when the number of carbon atoms is equal, for example, ethyl acetate and methyl ethyl ketone have specific volatilities close to 1 and form a minimum azeotrope with each other, so it is impossible to completely separate them by simple distillation. For this reason, no advantageous separation method has been found. j If one of the mixtures of ester and ketone is easily soluble in water, such as acetone, and the other is sparingly soluble, such as methyl acetate, these two components can be separated by extracting the acetone with water. Separation is relatively easy, but when both 7 are sparingly soluble in water, such as Co or higher esters and ketones, separation of this mixture is not easy.

Therefore, one method in such cases is generally to add a suitable oil and perform extractive distillation, but no suitable extractant that can be separated advantageously has been found so far.

As a result of various studies on this point, the present inventors discovered that it is possible to completely separate a mixture of ethyl acetate and methyl ethyl ketone at any mixing ratio by an extractive distillation method using water as the third component, and completed the present invention. I came to the point.

An example of extractive distillation using water as an extractant is a method for separating water-soluble alcohols and esters.
No. 75, but as in the present invention, each has the property of being sparingly soluble in water, each being azeotropic with water, and having volatilities close to each other, or forming a minimum azeotrope. No example has been found of separating a mixture of ester and ketone having the following by extractive distillation using water as an extractant.

The present invention uses a mixture of ethyl acetate and methyl ethyl ketone, which has conventionally been considered difficult to separate, as an extractant and is the cheapest.
The object of the present invention is to provide an industrially advantageous method in which the respective components can be separated by relatively simple operations by extractive distillation using water, which is easy to process thereafter.

Solvents that can be advantageously applied to the present invention include a mixture of ethyl acetate and methyl ethyl ketone, which have already been used in the explanation as C4 compounds, a mixture of one type of C5 propyl acetate and one type of pentanone, and a mixture of one type of C5 propyl acetate and one type of pentanone. It is a mixture of one type of butyl acetate and one type of hexanone, and some examples are shown in Table 1.

These mixed solvents are mixtures of acetic esters and ketones having the same number of carbon atoms, and ketones generally have a higher solubility in water and a higher azeotropic point with water. If the number of carbon atoms is C or more, the solubility in water becomes low, and the practicality of extractive distillation using water as an extractant decreases. The solvent targeted by the present invention is a mixture of acetic ester and ketone having the same number of carbon atoms between C4 and C6 in any ratio, and may also contain water.

A feature of the present invention is that water is used as an extractant when separating the above-mentioned mixture of acetate and ketone by extractive distillation. By extractive distillation in which a large amount is added to prevent the formation of water and heated to a temperature close to the boiling point of water, an acetate containing water is obtained from the top of the column, and a ketone containing a large amount of water is obtained from the bottom of the column.

The dilute aqueous solution of ketones obtained from the bottom of the column is processed through a well-known recovery column and dehydration column to recover ketones, and most of the water separated here is refluxed to the top of the extractive distillation column and used for other purposes. Discard the parts. The acetic acid ester obtained at the top of the column and containing a small amount of water is likewise recovered by known methods. That is, after separating the acetate ester layer and the aqueous layer in a liquid-liquid separator, the acetate ester is led to a dehydration tower where it is dehydrated and recovered, and the aqueous layer is refluxed to the upper part of the extractive distillation tower. The amount of water added here varies depending on the type of solvent, composition, water temperature, solvent temperature, etc.

In short, it must be selected so that two liquid phases are not formed within the column. The method of the present invention will be explained below with reference to the drawings.

The figure shows one embodiment of the present invention. As a representative example, a mixture of ethyl acetate and methyl ethyl ketone, which are C4 compounds, will be used for explanation, but it can be applied to other mixtures in substantially the same way. In the figures, numbers indicate devices, and letters indicate fluids flowing through the respective locations.

A mixture of ethyl acetate and methyl ethyl ketone has the symbol A
It is fed to the middle stage of the extractive distillation column 1 as shown in .
However, it may of course contain water, and depending on the mixture composition and the feeding temperature conditions, there is an optimum feeding position. The amount of water B necessary for separation is supplied from the upper part of the extractive distillation column 1. Top steam E of extractive distillation column 1
is a mixture of ethyl acetate and water that separates into two liquids when cooled in the condenser 2. After separating into a phase C rich in ethyl acetate and a phase F rich in water in the liquid-one liquid separator 3,
The water-rich phase F can be refluxed to the extractive distillation column 1.
On the other hand, an aqueous solution D of methyl ethyl ketone is obtained from the bottom of the extractive distillation column 1. Although a reboiler may be used as a heat source for the extractive distillation column 1, it is also possible to omit the reboiler by directly blowing steam from the steam blowing vibe 4 as shown in the figure. In this way, from the top of the extractive distillation column 1, a mixture of ethyl acetate and a small amount of water C1
An aqueous solution D of methyl ethyl ketone is obtained from the bottom of the column, and the desired separation is achieved. Dehydration of each of these components can be easily accomplished by conventional azeotropic distillation methods. 5 and 6 in the diagram
are dehydration devices for methyl ethyl ketone and ethyl acetate, respectively, and P and G are dehydrated methyl ethyl ketone and ethyl acetate, respectively. Next, the method of the present invention will be explained with reference to Examples.

All parts in the following examples are volume parts. EXAMPLE As the extractive distillation column (1 in the figure), a two-plate perforated distillation column was used.

A mixed stock solution of ethyl acetate and methyl ethyl ketone was fed to the 15th stage from the top at a rate of 185 parts/hour, and water as an extractant was fed from the top of the column at a rate of 76 parts/hour. Table 2 shows the results when the distillation amount was 100 parts/hour. As described above, according to the present invention, ketones and esters, such as a mixture of ethyl acetate and methyl ethyl ketone, which were previously difficult to separate, can be easily separated by extractive distillation using cheap heptavalent water as an extractant. , which can be further refined and is extremely advantageous industrially. In addition, in the present invention, other systems shown in the separation example of ethyl acetate and methyl ethyl ketone, such as mixtures of propyl acetate-methyl-n-propyl ketone, propyl acetate-methyl 9-isopropyl ketone, and propyl acetate-diethyl ketone, have the lowest azeotropy with each other. Although they form a mixture and the relative volatility of the ester relative to the ketone is close to 1, they can be separated by the method of the present invention.

[Brief explanation of the drawing]

The figure is a process diagram showing an example of implementation of the method of the present invention. 1... Extractive distillation column, 2... Condenser, 3
...Liquid-liquid separator, 4...Steam blowing vibrator, 5...Methyl ethyl ketone dehydration device,
6... Ethyl acetate dehydration equipment, A... Ethyl acetate and methyl ethyl ketone mixed stock solution, B...
・Water, C... Ethyl acetate containing a small amount of water, D.
...Methyl ethyl ketone containing a small amount of water, E...
...Tower overhead steam, F...Water containing a small amount of ethyl acetate, G...Dehydrated ethyl acetate, H...
...Circulating water, I, J...Drained water, P...
...Dehydrated methyl ethyl ketone.

Claims (1)

[Claims] 1. A mixture of acetic ester and ketone having 4 to 6 carbon atoms in the molecule and having the same number of carbon atoms is separated by extractive distillation using water as an extractant. A method for separating esters and ketones. 2. The method for separating esters and ketones according to claim 1, wherein the acetate ester and ketone are acetate ester and methyl ethyl ketone. 3. The method for separating esters and ketones according to claim 1, wherein the amount of water used as the extraction agent is such that no two liquid phases are formed in the column.